How would you feel if your boyfriend/husband donated his sperm without telling you?

My boyfriend and I are having a hard time working out a problem. I understand that we are not going to see eye to eye all the time but he thinks I am being very irrational. My boyfriend failed to tell me that he is a sperm donor and does not see the problem. Recently I asked him what he was up to and he dropped the bomb through text, that he had “just donated his seed to a lesbian couple”. I am not mad about him being a donor and I do not wish to control him. What hurts is the fact that he did not sit me down and just tell me. He waited until after it was done to tell me and I was far from prepared. If he can tell me how many people he has had sex with before me, he can tell me that he has donated or planned to donate his sperm. He thinks I am just being emotional and that it is none of my business because it does not effect me. I’ve explained to him in the best way I can what I am feeling but he won’t look at things from my point of view. I support him and love him but in this situation I feel disrespected and like trust was broken. I am fully aware that if his sperm works for the couple, the child will not be ours, but that will still be his biological kid(s) that will one day walk the Earth. That is nothing to brush off. Do you think I am being too emotional or do you think I have the right to feel hurt and angry? Please tell me how you would feel if your partner donated without telling you.

P.S. He is aware that I am asking for opinions anonymously. Thank you in advanced!